Tool / Drill Bit Demagnetiser

The End Result

 

The Build
 
The downside to the magnetic drill bit organiser that I created in the last post is that the drills themselves end up becoming magnetised.

This isn't really a problem for woodwork, but can get a bit annoying for drilling metal, so I started looking at building a demagnetiser.

Research online showed lots of examples (such as this) of powered demagnetisers, often using dismantled power transformers, mains power and over-heating risks, which was a bit off-putting.

However, there are passive (unpowered) demagnetisers available to purchase, so there must be another way.

It's well known that metal can be magnetised by rubbing it against a magnet. There is, of course, a lot of dry and boring scientific explanation about why it happens, but in layman's terms, the punchline is that metal stuff gets magnetised when the electrons in it get aligned. So to demagnetise it, just screw up their alignment. Simple, right?

Yeah, really, it is. If putting a bit of metal near one magnet pulls the electrons into line and magnetises it, sit the metal between two strong magnets, and the electrons can't agree which way to point, so they end up pointing in conflicting directions, and become demagnetised.

The magnets were provided courtesy of an old, broken hard drive. Unfortunately the shape of the drive magnets is a bit awkward to work with. To overcome this I took photos of the magnets, imported the photo into Inkscape and drew around them, exporting the resulting SVG into blender to turn into a 3D model for printing (a similar process that I used in this post)

The HDD magnet, and the shape drawn around it in Inkscape, ready for extrusion into Blender.

A photo posted by Anthony (@darkmidnight_diy) on Nov 27, 2016 at 1:00pm PST

A bit of hot glue was used to fix the magnets in place, and they were covered with Sugru to avoid tools just sticking straight to them.

To join the halves together, I would typically just glue them together, but this time I wanted to test a technique I've not tried before - plastic friction welding. It sounds fancy, but can be done with a Dremel and a bit of 3D printer filament - see the clip below for an example. I used orange filament against the black used for the printed body of the demagnetiser - it's not the most aesthetic choice, but it does help highlight the plastic weld technique a bit more easily.

 

The resulting join is plenty strong enough - as evidenced by several spontaneous shock tests, and totally not by accidental dropping.

The demagnetiser works simply by waving a magnetised tool through the gap in the gadget, as seen in the video at the top. It won't necessarily remove magnetism entirely, but as you can see, it significantly reduces it.

Magnetic Drill Bit Organiser

I'm forever losing drill bits, particularly the smaller ones in my workshop. While it's very much a "first world problem", the delay it causes to a project's schedule can be a huge pain, so this project uses some magnets from old dismantled hard disk drives.

Be warned - these magnets are very strong - putting them near your bank cards or anything else that's sensitive to magnetic fields is probably a really bad idea.

The plan is to magnetise a steel bar with the old hard disk magnets, mount it to the wall near my drill press so that I can keep drill bits and other small metal objects nearby and secured, and hopefully not lose as many.

The build
I started with a pine slat reclaimed from an old bed frame.

I didn't have a specific size in mind for this project, but the steel I purchased came in 1 metre lengths, which seemed a bit much, so I halved it and decided to base it around a 500mm steel bar.

The wood was cut to 55cm (allowing a 2.5cm margin) each side of the steel for mounting holes.

I measured out where the steel would sit, and drilled out a 3 grooves in the wood equally along where the steel would sit (so that the steel would cover the grooves).

In order to make the hard disk magnets fit within the boundaries of the steels measurements, some parts had to be cut down, which I did by using a grinder disk.

In hindsight this might not have been the smartest move, as the magnets would get hot from the friction and heat affects the magnetism of metal, and so this might have altered the effectiveness of the magnets.

In reality though, there was not a noticeable difference in their strength before and after trimming them.

The magnets were screwed into the wood so that they would sit in the drilled grooves, but the magnets themselves would sit in contact with the steel bar.

A photo posted by Anthony (@darkmidnight_diy) on Nov 15, 2016 at 1:22pm PST

A slight groove is cut into the wood along the length of the steel bar, so that the bar will sit flush with the wood, and attach the bar to the wood with a bit of glue. The magnets will hold it in place while the glue sets.

The bar will be magnetized by the underlying magnets, although wiping the bar with another magnet can strengthen the field, it will always be strongest nearest to the magnets themselves.

Finally a bit of wood stain, mount it to the wall, and done.

A photo posted by Anthony (@darkmidnight_diy) on Nov 16, 2016 at 1:48pm PST